Transistorized ignition device of an internal combustion engine

ABSTRACT

A transistorized ignition device for an internal combustion engine. A dc power source, an engine switch, a grounded contact point, an ignition coil, and an ignition transistor are connected in series for supplying an electric current to a primary winding of said ignition coil from said dc power source when the circuit is conducting. A controlling transistor is coupled in the circuit for controlling the operation of the ignition transistor, the controlling transistor being switched according to opening and closing of the contact point and holding the ignition transistor in a non-conducting state when the contact point is in an open position. A capacitor is connected in parallel with the contact point and is charged when the contact point is in the open position. The capacitor is further connected to the output of the controlling transistor, and a diode is connected between the capacitor and the contact point in the forward direction relative to the charging current for the capacitor. Upon the closing of the contact point the ignition transistor is made conductive by means of the charge on the capacitor.

United States Patent 1 Tanaka 1 Aug. 7, 1973 1 TRANSISTORIZED IGNITION DEVICE OF -AN INTERNAL COMBUSTION ENGINE [75] Inventor: Matsuo Tanaka,l-ligashi-Osaka,

Japan [73] Assignee: Nippon Denon Co., Ltd., Osaka,

Japan [22] Filed: Mar. 27, 1972 [21] Appl. No.: 238,454

[30] Foreign Application Priority Data Primary ExaminerLaurence M. Goodridge Assistant ExaminerCort Flint Attorney-E. F Wenderoth, V. M. Creedon et a].

[57] ABSTRACT A transistorized ignition device for an internal combustion engine. A dc power source, an engine switch, a grounded contact point, an ignition coil, and an ignition transistor are connected in series for supplying an electric current to a primary winding of said ignition coil from said dc power source when the circuit is conducting. A controlling transistor is coupled in the circuit for controlling the operation of the ignition transistor, the controlling transistor being switched according to opening and closing of the contact point and holding the ignition transistor in a non-conducting state when the contact point is in an open position. A capacitor is connected in parallel with the contact point and is charged when the contact point is in the open position. The capacitor is further connected to the output of the controlling transistor, and a diode is connected be-, tween the capacitor and the contact point in the forward direction relative to the charging current for the capacitor. Upon the closing of the contact point the ignition transistor is made conductive by means of the charge on the capacitor.

3 Claims, 2 Drawing Figures 5 4, 41 0 9 I L me: 11

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nuo'no PATENTED 3,750,638

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, PATENTEU AUG 7 I975 sum 2 BF 2 TRANSI STORIZED IGNITION DEVICE OF AN INTERNAL COMBUSTION ENGINE This invention relates to a transistorized ignition device of an internal combustion engine.

In a conventional transistorized ignition device of an internal combustion engine, an engine switch has at least three positions, namely neutral position in which the ignition device is not energized, a first ON position in which the ignition device is energized, and a second ON position in which a cell motor is energized.

In such conventional ignition device, the engine switch may be switched to said first ON position without causing trouble ifa contact point is in an open position at that time, and may be maintained in this first ON position for a long time unintentionally or for a particular purpose, for instance to listen to a radio installed in a vehicle.

However, if the engine switch is switched to said first ON position when the contact point is in a closed position a large electric current flows through an ignition transistor, and, therefore, if the engine switch is maintained in this first ON position for a long time, the ignition transistor is often destroyed owing to heat generated by the said large electric current.

Therefore, the object of the present invention is to provide a novel transistorized ignition device of an internal combustion engine which prevents flowing of large electric current through an ignition transistor regardless of whether a contact point is in an open or closed position when an engine switch is switched to said first ON position to thereby eliminate the defect of the conventional transistorized ignition device of the internal combustion engine as described above.

Hereinafter, the embodiment of the invention will be described in detail with referring to the attached drawings, wherein:

FIG. I is a circuit diagram of a conventional transistorized ignition device of an internal combustion engine; and

FIG. 2 is a circuit diagram of a transistorized ignition device of an internal combustion engine embodying the present invention.

At first, the conventional transistorized ignition device of an internal combustion engine is described with referring to FIG. 1.

FIG. 1 shows a circuit diagram of the conventional transistorized ignition device, in which a reference numeral I designates a dc power source for igniting the internal combustion engine. The dc power source I is connected in series with an engine switch 2 and a con tact point 3 which is grounded. 4, 5 and 6 are transistors. in which 6 is an ignition transistor which, in a conducting state thereof, supplies an electric current to a primary winding 71 of an ignition coil 7 from the dc power source I, and 4 is a controlling transistor for controlling an operation of said ignition transistor 6. Reference numerals 8 to 14 designate resistors, respec= tively, in which the resistor 14 is a ballast resistor for limiting dc component of the electric current flowing through the primary winding 71 of the ignition coil 7. A reverse voltage generated at the primary winding 71 of the ignition coil 7 is grounded through a diode 15. The reverse voltage is also attenuated by a capacitor 16. 17 is another capacitor for preventing generation of spark at the contact point 3.

In a circuit arrangement described above, when the engine switch 2 is switched to the said first ON position, and if the contact point 3 is in an open position at that time an electric current flows from the dc power source 1 through the engine switch 2 and the resistors 8, 9 and 10, and, therefore, a base voltage of the controlling transistor 4 is increased causing it to conduct. Therefore, a base voltage of the transistor 5 is lowered substantially to a ground voltage, and, therefore, the tran- 'sistor 5 does not conducts, and hence the ignition transistor 6 is also held in non-conducting state. Accordingly, an electric current does not flow through the primary winding 71 of the ignition coil 7.

However, if the contact point 3 is in a closed position when the engine switch 2 is switched to the said first ON position, an electric current flows from the dc power source 1 through the engine switch 2, the resistor 8 and the contact point 3. Therefore, the base voltage of the controlling transistor 4 becomes substantially to the ground voltage, so that the controlling transistor 4 does not conduct. Thus, the base voltage of the transistor 5 is increasedcausing it to conduct. Thus, the ignition transistor 6 becomes also conducted, and then an electric current flows through the primary winding 71 of the ignition coil 7. If the device is held at this state for a long time, a large amount of heat isgenerated due to a large electric current flowing through the transistors 5 and 6 and the primary winding 71, so that the transistors 5 and6 may be destroyed. Further, at the same time, a battery used as the dc power source I is over discharged and a power supplying ability thereof is lowered.

The device of the present invention eliminates such defects of the conventional ignition device, as described hereinbefore, and the embodiment of the invention is described in the following with referring to FIG. 2.

. In FIG. 2, the same or corresponding elements to those of FIG. I are designated by the same reference numerals as those of FIG. 1.

Referring to FIG. 2, a capacitor 18 is connected in parallel with the contact point 3. One terminal of said capacitor 18 is connected to an output terminal 41 of the controlling transistor 4 through a resistor 11, and to the ungrounded terminal of the contact point 3 through a diode 19 for preventing reverse current.

In a circuit arrangement as described above, if the engine switch 2 is switched to the said first ON position when the contact point 3 is in the open position, an electric current flows from the dc power source 1 through the engine switch 2 and the resistors 8, 9 and I0, and, therefore, the base voltage of the transistor 4 is increased. Therefore, the controlling transistor 4 is conducted and an electric current flows from the dc power source 1 to the controlling transistor 4 through the resistor 8, the diode I9 and the resistor 11. Accordingly, the base voltage of the transistor 5 becomes substantially to the ground voltage so that the transistor 5 does not conduct. Thus, the ignition transistor 6 is also held in a non-conducting state. Consequently, an electric current does not flow through the primary winding 71 of the ignition coil 7.

When the engine switch is switched to the said first ON position when the contact point 3 is in the closed position, an electric current flows from the dc power supply 1 through the engine switch 2, the resistor 8 and the contact point 3, so that the base voltage of the controlling transistor 4 becomes substantially to the ground voltage, and, therefore, the controlling transistor 4 does not conduct. Further at this time, the transistor S does not conduct, since the voltage at the output terminal 41 of the controlling transistor 4, and hence the base voltage of the transistor 5, are held substantially to the ground voltage through the contact point 3, the diode l9 and the resistor 11. Accordingly, the ignition transistor 6 does not also conduct.

As described above, according to the present invention, regardless of whether the contact point 3 is in the open or closed position, an electric current does not flow through the transistors 5 and 6 and the primary winding 71 of the ignition coil 7 when the engine switch 2 is switched to the said first ON position, and, therefore the defects of the conventional ignition device can be eliminated.

However, with this arrangement, the transistors 5 and 6 are kept still in non-conducting state even when the engine switch 2 is further rotated into the said second ON position in order to start a cell motor to open and close the contact point 3, and, therefore, the internal combustionengine does not operate. The capacitor 18 is provided to dissolve such a problem.

When the contact point 3 is in the open position, the capacitor 18 is charged in parallel with conduction of the controlling transistor 4; That is, when the cell motor is operated and thereby the contact point 3 is operated to open and close, the capacitor 18 is, charged during every opening of the contact point 3 by the dc power source 1 through the engine switch 2, the resistor 8 and the diode 19.

Now, when the contact point 3 is in the open position, the controlling transistor 4 is in a conducting state and the transistors 5 and 6 are in a non-conducting state, respectively. During this period of time, the capacitor 18 is charged. When the contact point 3 is closed by means of the cell motor, the controlling transister 4 is put in a non-conducting state as described hereinbcfore. But, because the capacitor 18 is connected to the output terminal of the controlling transistor 4 through the resistor 11, the base voltage of the transistor 5 is increased and so the transistor 5 conducts. Then, the electric charge stored in the capacitor 18 is discharged as a base current of the transistor 5. At this time, the discharge current of the capacitor 18 does not flow to the contact point 3 because it is prevented by the diode 19. As described above, when the transistor 5 conducts the ignition transistor 6 also conducts and an electric current flows through the primary winding 71 of the ignition coil 7. Accordingly, a large voltage is induced at a secondary winding 72 ot the ignition coil 7. Such an operation is similarly carried out during usual operation of the internal combustion engine.

A discharging time constant of the capacitor 18 is determined by a capacitance of the capacitor 18 and a resistance of the resistor 11, and it is required that said discharging time constant is set to be larger than a period of time during which the contact point 3 is closed at the minimum rotation speed of the internal combustion engine. On the other hand, a charging time constant of the capacitor 18 is determined by the capacitance of the capacitor 18 and a resistance of the resistor 8, and it is required that said charging time constant is set to be smaller than a period of time during which the contact point 3 is opened at the maximum rotation speed of the internal combustion engine.

As described hereinbefore, according to the present invention, when the engine switch is switched to the said second ON position the transistors are not destroyed regardless of whether the contact point is in open or closed position at that time.

What I claim is:

l. A transistorized ignition device of an internal combustion engine comprising a series connection consisting' of a dc power source, an engine switch, and a grounded contact point, an ignition coil, an ignition transistor for supplying an electric current to a primary winding of said ignition coil from said dc power source when beingconducted, and a controiling transistor for controlling an operation of said ignition transistor, said controlling transistor being switched according to opening and closing of said contact point and holding said ignition transistor in non-conducting state during said contact point is in an open position, characterized in that it comprises a capacitor connected in parallel with said contact point and adopted to be charged during said contact point is in the open position, said capacitor being further connected to an output of said controlling transistor, and a diode connected between said capacitor and said contact point in a forward direction relative to a charge current of said capacitor, wherein at closing of said contact point said ignition transistor being put in a conducting state by means of the charged voltage of said capacitor.

2. A transistorized ignition device of an internal combustion engine according to claim 1, characterized in that a discharging time constant of said capacitor is larger than a closing time of said contact point at minimum rotation speed of the internal combustion engine.

3. A transistorized ignition device of an internal combustion engine according to claim 1, characterized in that a charging time constant of said capacitor is smaller than an opening time of said contact point at maximum rotation speed of the internal combustion engine.

1! I! i i 

1. A transistorized ignition device of an internal combustion engine comprising a series connection consisting of a dc power source, an engine switch, and a grounded contact point, an ignition coil, an ignition transistor for supplying an electric current to a primary winding of said ignition coil from said dc power source when being conducted, and a controlling transistor for controlling an operation of said ignition transistor, said controlling transistor being switched according to opening and closing of said contact point and holding said ignition transistor in non-conducting state during said contact point is in an open position, characterized in that it comprises a capacitor connected in parallel with said contact point and adopted to be charged during said contact point is in the open position, said capacitor being further connected to an output of said controlling transistor, and a diode connected between said capacitor and said contact point in a forward direction relative to a charge current of said capacitor, wherein at closing of said contact point said ignition transistor being put in a conducting state by means of the charged voltage of said capacitor.
 2. A transistorized ignition device of an internal combustion engine according to claim 1, characterized in that a discharging time constant of said capacitor is larger than a closing time of said contact point at minimum rotation speed of the internal combustion engine.
 3. A transistorized ignition device of an internal combustion engine according to claim 1, characterized in that a charging time constant of said capacitor is smaller than an opening time of said contact point at maximum rotation speed of the internal combustion engine. 